Hydraulic Top Link: Project Completed!

MadReferee · Mar 10, 2006

( I presonally am not worried about an increase of a couple of hundred psi in the continuous flow situation in a system that sees a couple of thousand when working hard. )

Pressure has nothing to do with it.

This is an open center system with fluid always flowing thru it at a certain gpm. You have restricted the continuous flow of the hydraulic system by 20%. At normal operating rpm, this will cause heat build up and premature failure of one or more components of your hydraulic system. As Jerry said, heat is a killer in hydraulic systems and having the continuous flow restricted causes heat which in turn causes failures.

zapper · Mar 10, 2006

Ok I am not committed to the Eaton 5gpm valve. What other valves do you reccomend and from where for my b2910? I appreciate any help or comments.

Henro · Mar 11, 2006

Pressure has nothing to do with it. 

Hi Mad Ref!

What you say in your second paragraph is right on I think. But there is a conflict with first statement. The pressure DROP certainly does have something to do with it, as that is the reason the excess heat will be generated. I know you said pressure, but Bill was referring to the pressure drop in the text you quoted.

 I presonally am not worried about an increase of a couple of hundred psi in the continuous flow situation in a system that sees a couple of thousand when working hard. 

Bill's comment surprised me at first, but since 200 psi out of 2000 is 10 percent, I guess that would be at least marginally acceptable. IF it is 200 PSI. Need to make a measurement to be sure...I would be concerned until I had hard facts to back up my feelings.

When I did my T&T I made sure that the valve I used was rated at more than my B2910 flow. Must be my conservative nature... /forums/images/graemlins/grin.gif

MadReferee · Mar 11, 2006

Henro, nice to hear from you again.

There will be some pressure caused by the restriction itself but it is clearly not the main concern for this scenerio.

The big concern is the fact that the flow path has been restricted by 20%. The pump is geared to produce a certain gpm output. By restricting the path you have now caused the pump to labor as it tries to continuously push x amount of fluid past an x-20% restriction. If the restriction approaches 100% the pump starts to labor harder and eventually dead heads and the result is an expensive repair.

I know we both used the same Prince SV valve for our rear remotes. As my post from 3 years ago noted, I investigated several valves and settled on the Prince SV as the best bang for the buck that met or exceeded the specs for the B2710/2910/7800.

I rejected the Eaton-Cessna that these guys are using because it was not rated for the flow of the B series Kubotas. However, the Eaton-Cessna is the perfect choice for any system with an implement flow of 5 gpm or less.

MadReferee · Mar 11, 2006

( Ok I am not committed to the Eaton 5gpm valve. What other valves do you reccomend and from where for my b2910? I appreciate any help or comments. )

Any valve in the 8-12 gpm range will work just fine. Larger capacity valves tend to be too big and bulky to fit on the tractor.

I used the Prince SV and so did at least 4 or 5 others that I know about. It's the right form factor and meets or exceeds all the specs for use on the B2710/2910/7800/3030/2630.

Bill_in_MI · Mar 11, 2006

I think the way you are reasoning will always be "safe" for sizing. But I think it gives a bit of a distorted picture of what is really going on. I agree that avoiding the heat build-up is the bottom line here. But only in the neutral flow situation. Don't care about the work port restrictions...in fact it may be desirable in this application(better control) as long as system pressures are not exceeded. You cannot simply take the NOMINAL flow rating given by the manufacturers and calculate a percent restriction, or energy loss, etc. You need to view the flow performance curves to find out what the relevant situation is. In this case, the Eaton-Cessna folks made the call at 5 GPM for combined performance reasons...neutral flow drop, working port drops, etc. The neutral flow drop at 5 gpm is around 30 psi. This is the energy loss leading to whatever heating is contributed by the valve and what is boosting the overall neutral load on the pump and other components. A 10 GPM Prince loader valve (interestingly of the same in-out port sizes) allows around 100 psi drop at the max rating for neutral flow. I extrapolated the Eaton-Cessna curves out to around 7 GPM (I know...there is some danger here, but I work with system flow curves (blood not oil) almost daily) and the pressure drop looks to be about 100 psi...same as the Prince 10 GPM. So it's not all apples to apples. The way Mad is looking at it will always be conservative and safe. I'm walking on the "wild" side...I believe I am accepting a reasonable compromise to keep the nice small footprint I want.

Bill_in_MI · Mar 11, 2006

I ran a very unscientific experiment today. Let the engine run for two hours...first hour at idle and second hour at 2000 rpm and put an electronic thermometer on the Eaton Cessna valve block between the input and PWB. The temperature peaked and remained steady at 108 F. The oil in the transmission case as measured in the dip stick well was 100 F at the same time. It was a nice sunny day outside...about 55 F. For what it's worth, the seat was a nice comfortable 93 F on the surface. Don't know what this may mean to you all, but that's the info.